Graphics processing units (GPUs) often perform BLT operations to copy a region of a source surface to a region of a destination surface, or to composite corresponding regions of multiple source surfaces into a single corresponding region of a destination surface. A GPU may include specialized hardware for writing and reading surfaces to and from memory as part of the BLT operation. The GPU hardware for writing and reading surfaces may have various alignment constraints that need to be satisfied in order to successfully service a BLT command. If a BLT command does not satisfy such alignment constraints, then the GPU hardware may not be able to service the BLT command.